US1118910A - Automatic telephone system. - Google Patents

Description

3 5M I fizfremgggmm A. H. DYSON. AUTOMATIC TELEPHONE SYSTEM. APPLICATION FILED 0GT .13, 1910.

1,118,91OQ Patented Nov. 24. 1914b 5 SHEBT SSHEET 1.

A. H. DYSON.

' AUTOMATIC TELEPHONE SYSTEM. APPLIOATION FILED 00113, 1910.

1,1 18,919, Patented Nov. 24 1914.

5 SHEETSSHEET 2.

1 gm fiifeziylm' A. H. DYSON. AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED 001*.1a,1910'.

Patented 111017.24, 1914.

' 5 sums-sum: 3.

MEE mQ A. H, DYSON. AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED 00113, 1910.

Patented N0v.24;,1914.

5 SHEETS-SHEET 4.

A. H. DYS'ON.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED 0GT.13, 1910.

Patented Nov. 24, 1914.

'5 sums-4mm 5.

UNITED STATES PATENT OFFICE.

ALFRED H. DYSON, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SWITCI-IBOAR-D AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Nov. 24, 1914.

Application filed October 13, 1910. Serial No. 586,817.

'1 '0 all whom it may concern:

Be it known that I, ALFRED H. Dxsox, a citizen of the United States of America, residing in Chicago, county of Cook, and State of Illinois, have invented certain new. and useful Improvements in Automatic Telephone Systems, of which the following ments which are more positive in operation and simple of construction.

Another object is to provide an improved metallic trunk circuit for connecting subscribers indifferent exchanges which is adapted by rapid interruptions of its circuit caused by the originating subscriber to operate switches in the distant exchange to extend the line of the calling to the called subscriber.

Referring to the accompanying drawings, Figure 1, which includes parts 1, 2, 3 and 4 illustrates diagrammatically an automatic telephone system constructed in accordance with my invention. Figs. 2, 3 and 4 are front and side elevations of a selector switch adapted for use with the circuits of my invention. Fig. 5 is a, plan view of Fig. 2, showing more particularlythe offnormal spring arrangement. Fig. 6 is a cross-section along the line 66 of Fig. 2 looking in the direction of the arrow indicated on said Fig. 2. I

Referring .now more particularly to Fig. 1, A shown at the left of Fig. 1, designates a subscribers station united to an exchange by line limbs 1 and 2 which terminate in multiple contacts of line selector and conlished between said subscribers -stations A- and B through the line circuit C, line selector D, first selector E, trunk circuit F and its connected second selector G, third selector H, connector J and line circuit C associated with the subscribers line B.

The' system illustrated in Fig. 1, is adapted for one hundred thousand lines, and assuming such a system divided into several exchanges, the trunk circuit F is adapted for connecting subscribers in one exchange with subscribers in another exchange. In establishing a connection between callin substation A and called substation B, and assuming the lines of the saidsubstations terminate at different exchanges, upon the removal of the receiver of the subscriber at A from its switch hook upon the initiation of a call, circuit changes are effected at line circuit C. Responsive to said circuit changes, master switch K starts an idle line selector D to seek out and connect with terminals of the calling line. The calling subscriber, after placing a coin in his coin device, actuates his calling device, whereby the first selector E connects with an idle trunk circuit F leading to a second selector G of the distant exchange in which the line of the-called for subscriber terminatesl The next operation of the calling device is effective to cause the second selector, H, having access to the group of one thousand lines with which the called line is associated. Upon the next operation of the calling device, the third selector H extends lector G. to connect with an idle third sethe connection to an idle connector J of the group of one hundred lines with which the called line is associated. The next two operations of the calling device cause the connector J to step its wipers into connection with the terminals of the called line, Which if idle, is automatically rung. If'the called line is busy, the calling subscriber receives a characteristic busy signal, and he may then, by replacing his receiver upon its switch-hook, restore the switches which were used in establishing the connection and have his coin returned. If the'called line isv idle, the called subscribed in response to the calling signal, removes his receiver from its switch-hook, thereby cutting 'ofi'the ringing current. Upon the termination of conversation, the subscribers, by replacing their receivers upon their switch-hooks, release the apparatus which was used in establishing the connection and it is then available for further use;

' The subscribers station A is a coin-controlled device in which it is necessary for the calling subscriber to deposit a coin or token before being able to establish a connection with a called subscriber. The subscribers substation includes the dial 3 and the impulse springs 4. The said dial 3 is normally locked against actuation by magnet 5. The off-normal springs 6 are adapted .to

, be closed while the dial 3 is off normal. The

impulse springs 4: are normally shunted by the normal contact 7. The substation telephone circuit of A. is the well known Kellogg circuit having a switch-hook 8 which normally closes a circuit through the call bell 9 and the condenser 10,.-while the coil of magnet 5 also serves as an impedance coil. Upon removing the receiver 11 from the said switch hook 8, the call bell 9 is removed from the circuit and the transmitter 12 and receiver are cut in.

The calling device 3 is normally locked against actuation by magnet 5, and is not unlocked until the line has been selected by be selected by a line selector D, it is impossible to complete a connectionto a called subscriber until the shunt spring 7 is d1s connected by dropping a coin or token in slot 54.

The substation A is connected with the exchange by the line limbs l and 2, the said limbs terminating at a line-circuit C. Each line circuit C comprises a line relay LR which is adapted upon. the initiation of a call to start through the medium of a master switch K, an idle line selector D to connect to a calling line. The cut-off relay CO is adapted to be energized when its line is connectcd to remove the substation control of relay LR.

Each line selector D includes a primary magnet PM which is adapted to move the wipers of the line selector in a primary direction to select the group of ten lines with which a-ealling line is associated. The said magnet PM is controlled by the primary busy relay PER while the secondary busy relay SBR- controls the actuation of the secondary magnet SM, the said magnet SM being adapted to move the wipers of the line selector D in a secondary direction to con- 14: and 15 respectively.

nect with a calling line. Each line selector D also includes'a release relay RR and a release magnet RM, the said relay and magnet coiiperating to release the line selector D when adisco-nnection is desired. Each line selector D also includes the primary ofli-normal springs PON which are adapted to be moved to their alternate position upon the first primary movement of the switch, while the secondary cit-normal springs SON are adapted to be moved to their alternate posi- For each group of one hundred lines and associated ten line selectors, a master switch K is provided. Each master switch K is controlled by the hundred lines with which. it is associated,'it being adapted to start an idle line selector D to seek connection with a line upon the initiation of a call. The switch construction of master switch K includes several banks of contacts disposed in a circle,

each bank having a wiper adapted for connection with its contacts. mounted on a shaft havinga ratchet wheel secured thereto. The motor magnet MM includes an armature withthe ordinary pawl to engage the said ratchet wheel to' rotate the wipers when the said magnet MM is operated. in one direction only as the contacts are arranged in a complete circle. This construction is well known and a further description thereof is unnecessary. The relay 19 of the master switch K is also common to the hundred lines controlling the said master switch, all of the said lines being connected to the said relay at the common point 2i).

The bank contacts 13, 14: and 15 of each line selector D are divided into ten groups of ten each, and the one hundred subscribers lines which terminate in the said bank conta'cts are therefore also divided into ten groups of ten each. Eaclr group of ten line circuits C has a common relay 21,-each of the ten line circuits being connected to the associated relay 21 at commonpoint'22. Each group of ten bank contacts-has a group'con tact 23 which is adapted to cooperate with the group wiper 24:. Each of the rouper tacts 23 is normally grounded at its ease-- eiated relay 21, and when any line is calling, its group relayIQl removes the ground from the contact :23 for the purpose of controlling The wipers are Thus, the wipers are advanced a selection of that certain group by the wipers 16, 17 and 18. I

Each first selector includes a primary relay PR for transmitting the primary operating impulses, a secondary relay SR for transmitting secondary impulses, a primary magnet PM, a secondary magnet SM, a release relay RR and a release magnet RM for releasing the switch. Each first selector E also includes a busy or trunk selecting relay BR which is adapted to control the selection of an idle trunk; The reversing relay RV which is operated when a called subscriber responds is adapted to reverse the battery supply over the calling subsoribers line for the purpose of actuating coin controlling or meter mechanism. The primary olf -normal switch FUN and secondary off-normal switch SON are adapted to be moved to first respective elf-normal movements of the switch. The wipers 25, 26 and 27 of each first selector E are adapted to cooperate with the bank contacts 28, 29 and 30.

The trunk circuit F which is multiply connectedto the bank contacts '28, 29 and 30 of first selectors E, includes an :impulse repeating relay IR and the polarized relay 31 and relays and 33. The said trunk circuit F extends its pair of conductors 34 and 35 to a distant exchange where they terminate in a second selector G.

1 Each second selector G includes the usual primary relay PR, secondary relay SR, primary magnet PM and secondary magnet SM", a release relay RR and release magnet .i-M and a busy or trunk selecting relay BB The battery reversing relay RV is adapted to reverse the battery flow over the trunk circuit to operate the polarized magnet 31 of the trunk circuit F upon response of the calledfor subscriber. The primary cit-normal springs PON and the secondary oil-normal springs SON are moved to their alternate position upon the first respective movements of switch G. The wipers 36, 37 and 38 of second selector G are adapted to cciiperate with bank contacts 39, 40 and 41. The said bank contacts 39, 40 and 41 lead to third selcctor switches H, each third selector in cluding a. primary magnet PM a secondary magnet 8M release relay RR and release magnet RM and a busy or trunk selecting relay BB Each third selector H also includes a primary off-normal switch PON and a secondary off-normal switch SON the said switches being adapted to be moved to their alternate positions upon the first respective movements of switch H. wipers 42, a3 and 424 of third selector H are adapted to cooperate with their bank contacts 45, M5 and 47, the saidbank contacts leading to connector switches J.

Each connector switch J includes the their alternate position upon the The usual primary magnet Plv and secondary magnet 8M a release relay RR" and release magnet RM in addition to several other relays. Each connector J also includes primary elf-normal switch PO)?" and a secondary off-normal switch SON, each of. the said switches be Q moved to its alternate position on the t respective movement of switch J/ The pipers 48, 19 and 50 of each connector d have access to the terminals 51, 52 and of one hundred subscribers lines. The subscribers line B terminates at a line circuit C which is similar to the line circuit C, although all of the connections are not shown at C.

The telephone circuit of substation B is similar to that of A except that B has no coin controlling device in connection.

Uperatrbqa-Jiaving now given a general description of the character of the apparatus diagrammatically illustrated in Fig. 1, it is believed that the invention will be best understood by describing in detail the operation of the system as illustrated. Assuming now that the subscriber at telephone A desires to converse with the subscriber at telephone B whose number is'23456, the subscriber at a will remove the receiver 11 from its switclrhook 8, and thereafter place a coin or token in the slot 54:. The switchhook 8 moving upward, opens the lower contacts removing the shunt from the transmitter 12 and also disconnecting the call bell 9 from the line and connecting the upper contacts with the said switch-hook 3. The coin or token which is placed in the slot 54 moves downward until it rests upon the end of armature and engaging the insulating stud 56, moves the contact spring 7 to its alternate position. The opening of the normal contact 7 removes the shunt from the impulse springs 4, While the closing of the alternate contact-7 connects the winding of the polarized magnet 57 with the telephone line. At this time, however, the switch-hook 8 being in its upward position, the contact 58 is closed, thereby shunting the Winding of the polarized magnet 57 rendering it at this time inoperative.

The receiver 11 having been removed from its switch-hook, and said switch hook having moved to its alternate position, as described, a circuit is established through the line relay LR, traced from ground through the winding of the said relay LR,

normal contact 59, normal contact 60, line limb switch-hook 8, contact 58, impulse springs 4, the winding of coil 5, line limb 1, normal. contact 61 of cut-off relay CO, through protective resistance to battery. Line relay LR is thereupon energized, look; ing itself through contact 62, contact 63, the winding of the relay 19 to battery, this circuit also energizing the said relay 19. Also,

' relay 21 traced from ground at the said alternate contact 68, through the winding of said relay 21 to battery. The said relay 21 is thereupon energized removing the ground at contact 69 from. the group contact 230i the group of ten'li'nes in which the line of subscriber A is included.

- gized Although when the subscriber at removes receiver 11 from switch-hook 8, a'circult is established through th windingfloi coil5, the line relay having been, thereupon immediately energized, again opens thisfl'circult and the 'armatureiof said 'electroma et 5, should it be attracted,-'-immediately fills back, again locking the; calling device? Returning now to relay 19,,"which enerupon the closing of contact 62 of-the line relay LR, a circuit is-e'stablished from .ground at normal contact 70 of relay ;1, 3,

alternate contact 72 of relay 19, wiper contact 74, normal contact 75 of switch PON of line selector D,throu h the "winding of the primary busy relay. BR to battery. The relay PBR is thereupon energized, closing a circuit through the primary PM from ground at alternate contact 76, througlrthe winding of the said magnet PM to the ungrounded pole of alternating currentgeperator, 'The primary magnet is now energized into engagement with the first group contact 23 and also moves the wipers 16, 17 and 18 opposite the first group of bank contacts.

' As illustrated in connection with the line selector D, the line of the calling subscriber at A terminates at contacts in thegfourth group of bank contacts of said switch D.-

The first group having all idle lines connected thereto, there will be a direct ground upon its group contact 23 from normal contact 69'. of relay 2ll The relay PER is therefore looked over a circuit traced from said ground at contacts 69' contact 23, wiper 24, alternate contact 77, through the winding of PBR to battery. The wipers of the line selector D having taken a single step as described, the primary ofi -normal switch PON has moved to its alternate position, thereby opening the initial energizing circuit'for said relay PBR' at the contact of the said switch PONQ The relay QPBR having been locked in its energized position, to

ground at first group contact 23, the circuit energized and continues so until the 1 and advances the wiper 24 the said primary busy relay for the primary magnet PM is maintained and the said magnet steps the wipers 16, 17, v 18 and 24 to the next grou a This also grounded, the relay PB is main? mary magnet PM has advanced the r 0 2% into connection with the bank contact a3 of the group relay 21. The group relay 21 being energized and the ground being re moved from its contact 23 as described, the relay PER is deenergized, opening the cuit for the primary magnet PM and wipers 16, 17 and 18 remain in position opposite the bank or 'group of contacts which include the contacts 13, 14 and 15 of the calling line A.

At the time the relay 19 was energized,

, establishin an initial energizing circuit for the relay}. R, a circuit for the release relay BR 'was also established from the ground at' inormal contact 7 0 of relay Y1 at master switch K, the said circuit energizing the said relay RR which locked itself to the ground connection atthe secondary off-normal switchSON. The wipers 16, 1'? and 18 to having beenmoved to the group of contacts which/includes the line of subscriber Ajand the relay PER having been. deenergized, a circuit for the secondary lousy relay is established from ground at normal Contact 76 to alternate contact 7 8 of switch PON,'which moved to its alternate position upon the first primary step of switch D,

normal contact 79 of switch SON, through the winding of said secondary busy relay SBR to'battery. The said relay S333 is thereupon energized, closing a circuit through the secondary magnet SM from ground at alternate contact 80, alternate contactSl of relay RR and through the winding of the said secondary magnet SM to alternating ;generator. The secondary magnet Slifis' thereupon energized, advancing the wipers 16, 17 and-18 to connect with the first set of bank contacts in the selected group.

Assuming that the first set of contacts are the terminals of a non-calling line, the private contact 13 is connected with ground at normal contact 68 of line relay LR of the associated line circuit C, Due to said ground upon the first contact 13, a lockingcircuit is established for, the relay SEB- traced from the said groundover wiper-16, normal contact 82 of release magnetRM,

'and alternate contact 83 as relay'SBR to the calling line .A being energized, the

ground at contact 68 is disconnected from the bank contact 13 and the secondary busy relay 6BR finding no locking circuit,

advancing the wipers of the master switch K to the next idle line.v selector D which is accomplished as follows: Upon the said energization of relay 71, a circuit is closed from ground at alternate contact 70, through the winding of motor magnet MM to alternating current generator. The motor magnet MM is energized and advances the wipers 73 and 87 to the next set of contacts 74' and 86, and there being a ground upon the contact 86', relay remains energized and the motor magnet MM advances wipers 7 3 and 87 another step into engagement with contacts 74: and 86 which are contacts leading to another line selector D. If this line selector D is idle, there will be no ground upon the contact 86 and the relay 7-1 will denergize, opening the circuit for the. motor magnet MM and preventing any further advance of wipers 73 and 87. If the line selector which is connected to the contact 74 and 86 is busy, there will be a ground upon contact 86 and relay 71 remaining energized, wipers 73 and 87 are advanced until they reach the terminals of an idle line selector switch. Thus, it will be seen that as soon as a line selector contacts with the terminals of a calling line and relay SBR deenergizes, master switch K moves its wipers to connect with the starting terminals of the next idle line selector of the group. YVhen the secondary busy relay SBR became energized, a circuit for the primary relay of the first selector I) was closed through the alternate contacts 88 and 89 of relay SBR, the said circuit being traced from ground at primary relay PR of first selector E, through the upper winding of the said relay,'contact 90 of relay RV, conductor 91, contact 88, contact 92. of relay RR, contact 89. of relay SBR, conductor 93, contact 94 of relay RV, the

. lower winding of relay PR to battery, energizing the said relay PR and closing its alternate contacts.

Vhen the line selector switch D starts on its secondary travel to select the calling line A, the secondary off-normal switch is moved to its alternate position, opening the initial locking circuit for relay RR- and establishing a new locking circuit from ground at alternate contact 95 of relay PR of first selector E, conductor 96, alternate contact 97 of secondary off-normal'switeh SON, alternate contact 98 of relay RR, through the winding of-the said relay to battery, locking the said relay RR in its energized condition. Upon the de'energi'zation of the secondary busy relay S BR, after the line A'has been selected, a circuit for cutoff relay, CO is established, being traced from ground at the upper Winding of relay PR at the first selector E, contact 90 of relay RV, conductor 91, contact 99; wiper 17, contact 14, contact 101 of cut-off relay CO, through thewinding of said relay CO to battery. The said relay CO is thereupon energized and .a locking circuit is established from battery through the winding of relay CO, alternate contact 102, conductor 103, bank contact 18, wiper l6, and normal contact 82 to ground at normal contact 83. The series locking circuit for the line relay LR and the master switch relay 19 is opened at contact 63 upon the cnergization. of cutoff relay CO, thereby restoring the said relays LR and 19 to normal. The restoration of contact 68 of relay LR to normal opens the circuit for group r'elay 21 which is decnergized, again placing ground upon its group contact 23. Should some other line in the group of ten with which the calling line is associated be calling, the group relay 21 remains energized, keeping its contact 23 ungrounded until any other calling lines in the group have been selected. The restoration of the contact 64 of relay LR to: normal, removes the initial ground connection from the multiple contacts 65 at the connector switches having access to line A and replaces this initial busy ground by a connection from. the ground which looks cut-off relay CO. Upon the said energization of cutoff relay CO, alternate con tact 60 is closed, thereby extending the line of subscriber A to the first selector E and also establishing a circuit for the primary relay PR over the line, the said circuit being traced from the ground at the upper winding of said relay PR, contact 90, conductor 91, normal contact 99, wiper 17 bank contact 14, alternate contact 60, line limb 2, switch hook 8 and contact 58, impulse springs 4-, electromagnet 5, line limb 1, contact 15, wiper 18, normal contact 100, conductor 93, contact 94:, the lower winding of relay PR to battery. The primary relay PR is now energized over the line of the calling subscriber at A, this circuit also energizing the magnet 5, thereby attracting its armature and unlocking the calling device 3.

At the time rimary relay PR was energized, as described, a circuit was established through the release relay RR of first selector E, traced from ground at alternate contact 95 of relay PR, normal contact 104 of relay Ry, through the winding of the said the called subscriber terminates.

relay RR to battery, energiiting the said relay. The subscribers station at A now having had its line conductors extended to the first selector E, the subscriber now operates the calling device 3 in a clockwise direction until two of the insulated projections have passed the impulse springs 4. The movement of the device 3 off-normal closes the spring 6, shunting the coil 5 while the impulse springs 4 are being-operated. The subscriber having advanced the device 3 as described, releases it and it restores to normal by the spring shown thereon, opening and closing the impulse springs 4: two times. This interrupts the previously described circuit through the primary relay PR of, the first selector E two times, decnergizing and energizing said relay to transmit two impulses. It will be remembered that the ground at contact 95 of relay PR established a locking circuit for the release relays RR tion from the impulses transmitted by pri- Jmary relay PR and does not retract its armature until said primary relay PR has ceased to vibrate. Upon the said deenergization of relay PR a'circuit is also established through primary magnet PM. traced from the said ground at alternate contact 105 of relay RR, normal contact 10? of relay PR, conductor 108, conductor 189, normal contact 110 of oft-normal switch SON, through the winding of said primary magnet PM to battery, energizing the said mag net. The relay PR is immediately energized, again opening the circuits through. the secondary relay SR and the primary magnet PM, followed by another deenergization of said relay PR to transmit another impulse through the said relay and magnet. Thetwo impulses transmitted through primary magnet PM serve to step wipers 25, 26- and 27 to a point adjacent the second group of contacts. The said group of contact' iconnected with trunk circuits F extending to the exchange in which the line of After the second operation of primary rela PR, the circuit through the secondary re ay SR is opened lon enough for said relay SR to de- ',-energize. ponthe said denergization of relay SR a'secondary impulse transmitted through tliebusy or trunk selectin relay BB, the said circuit being trace from said secondary magnet SM to alternating generator.. The secondary magnet SM is thereupon energized and steps wipers 25, 26 and 27 into engagement with the first set of contacts in the selected group. If the first set of contacts leads to a busy trunk circuit F, there will be a ground upon the contacts 28 as will be hereinafter described, and a locking circuit for the relay BB is established from the said ground at contact 28, Wiper 25, contact 118 of magnet RM, alternate contact 119 of relay RR, alternate contact 120 of relay BR, through the winding of said relay BR to battery. The said relay is locked in its energized condition and secondary magnet SM steps wipers 25, 26 and 27 to the next set of contacts in the group. Should the second set be busy, relay BR will remain energized, and secondary magnet SM will step the wipers to the next set of contacts and so on, until relay BR finds an ungrounded or idle contact 28. As soon as thc'wipers 25, 26 and 27 connect with an idle set of contacts, the relay BB is denergized opening the circuit for the secondary magnetSM andpreventing any further advance of said wipers 25, 26 and 27.

Upon the first secondary ofl:'-normal movement of the switch E the switch SON is moved to its alternate position, opening the initial. energizing circuitfor relay BR", but the said switch SON is so adjusted that the wiper 25 connects with the first contact 28 in the group before the contact 11 1 of the said switch SON is opened. Thus, a loching circuit is established for relay. BR at contact 28 if the first set of contacts is busy before the initial energizing circuit for the said relay is opened.

To prevent the subscriber from again actuating the calling device 3 before the first selector E has selected an idle trunk. and

probably sending a false number of impulses, relay 113 is provided to short circuit calli.ng.device 3 against actuation. The secondary impulse which initially energized relay BR as previously described, flows through the windings of relay 113 as pre is moved to its alternate position, but at this time the relay BR being energized, a new circuit for said relay 113 is established from alternate contact 105.

battery at alternate contact 122 of relay BR, conductor 123, the Winding of said relay 113, normal contact 112, normal contact 111, alternate contact 10.6 to ground at The last traced circurt forthe relay 113 is maintained until the said relay 113 busy-relay BB is denergized, opening the alternating contact. 122, and allowing the to denergize and open the contact 121. The previously traced shunt is thereby opened. and the path for battery through the relay PR is again established over the line of the calling subscriber. The magnet 5 is thereupon energized, attracting its armature and again unlocking the calling device 3. Upon denergization of relay BR, "after selecting an idle trunk circuit F a busy or grounded condition is established ,at the multiple contacts 28 traced from ground at normal contact 1200f relay BR, alternatec'ontact 119 of relay RR, normal contact 118 of release magnet RM, wiper 25tand contact 28. Thus, the selected trunk circuit F will be maintained busy against selection by any other firstselector. Also, upon the deinergization of relay BR, energizing circuit for relay 33 of trunk circuit F is established from ground at alternate contact 105 of relay RR of first selector E, alternate contact 106, normal contacts 111 and 112, Winding ofrelay 113, normal contact 122, Wiper 27, contact 30, contact 123, the winding of said relay 33 to battery. The said relay 33 is thereupon energized opening its initial energizing circuit and locking itself over contact 12% to ground at bank contact 28. Upon the said energize.- tion of relay 33 the contact 125 is closed, establishing a circuit for primary relay PR of second selector G traced over the following path: from ground through the lower Winding of said relay PR, contact 126, contact 128, conductor 35, alternate contact 125, the Winding of polarized relay 31, norrnal contact 129 of impulse repeating'relay IR, normal contact 130, conductor 34:, conductor 131, contact 132, contact 133, the upper winding of relay PR to battery. The relay PR is thereupon energized, but the flow of battery through the polarized relay 31 is in a direction tending to hold the armature 134 against the lower contact.

' of the previously 'device 3 to open and close the contacts 4 three times, thereby interrupting the previously described circuit through the relay PR three times. Three primary impulses are thereby transmitted from ground at alternate contact 105 of relay RR, normal contact 106, the Winding of secondary relay SR to battery, energizing the said relay and holding its armature in an attracted position until after the said impulses have been sent through its Winding. The said impulses from ground at alternate contact 105 are also conducted through normal contact 107, conductor 10.8, normal contact 136, Wiper 26, contact 29, normal contact 137 of relay 32, through the Winding of impulse repeating relay IE to battery. The said three impulses energize and deenergize the said relay IR three times, opening and closing the contact 129 three times. The opening of contact 129 causes three interruptions described circuit through relay PR of second selector G, de'e'nergizing and energizing said relay PR three times. Due to this deenergization and energization of the said relay PR three impulses are transmitted from ground at alternate contact 133 of relay RR through normal contact 139, and the Winding of the secondary relay SE to battery, energizing the said relay SR which retains'its armature in an attracted position due to its sluggish construction, until after the three impulses have been transmitted through its 3 Winding. The said three impulses from v tlieground at alternate contact 138 also energize and deenergize rimary magnet lPlVl over a circuit traced rom the said ground at alternate contact 138, normal contact 140, V

B is associated. Upon the first primary offnormal movement of switch G. contacts PON are moved to their alternate position and a circuit for sluggish relay 143 is esadvances the wipers 36, 3f and 38 into con-1 nection with the first set ofcontacts in the selected group. If this first set is busy '1 there will be a' ground upon the contact 3% as will be hereinafter described and relay BR? will be retained in its energized c'onditablished from ground at alternate contact 14 1- of primary oil-normal switch PQN normal contact 145, the winding of said re lay 148 to battery, energizing the said relay and opening contact After the last of said impulses has been transmitted by primary relay PR of the second selector G, the secondary relay SR is deenergized and a secondary impulse is transmitted from ground at contact i l-7 of relay 148, impedance. coil. 149, normal contact 150, alternate contact 151 of switch PGN", normal contact 152 of off-normal switch SQN through the winding of the busy relay to battery, energizing the said. relay BB Upon the said eriergization of relay Bila circuit through secondary magnet SM is established from ground at alternate contact 153, through alternate contact 154, the winding of secondary magnet SM to alternating generator. ary magnet SM is thereu on energized and tion over a circuit traced from the said ground at the first contact 39 in the group,

wiper 36, normal contact 154-, alternate contact 155, alternate contact 156, through the winding of said relay BB to battery. -The secondary magnet 8M then stops the wipers 36, 37 and 88 into engagement with the next I set of contacts 39, 40 and 41 leading to a third selector similar to H. If this switch is busy, its private contact 39 will be groundcd or in a busy condition and relay BB remainin locked secondar Ina net SM advances the wipers 36, 37 and 38 to the next set of contacts and so on until the contacts 39, 40 and ell of an idle third selector switch H are engaged. Assuming the third selector switch H shown is idle, contact 39 is ungrounded and relay Blx decnergize's, opening the circuitfor secondary magnet 5M at Contact 153, thereby presenting any further adr ance of wipers 36, 37 and 38.

The secondary off-normal switch SON is moved to its alternate position on the first secondary movement of switch G, thereby opening the initial energizing circuit for relay BR and also cutting off primary magnet PM fIOmfiOHDQCllOD. with the conductor 141. Also, upon the dcencrgization of relay BR a ground or busy condition is placed upon the multiple contacts 39 traced'from ground at normal contact 150 of relay BB through alternate contact 155, normalcontact 154, wiper 36 to contact 39 and its multiples. This busy or ground condition of the contacts 39 renders them unselectable, by any other switch seeking access to a third The said secondselector in the same group with the third selector H.

The line of the subscriber A has now. been extended to a third selector H which has access to the group of one thousand lines with which the called subscriber is associated. The subscriber at A now actuates the calling device 3 to'interrupt the previously described circuit through the primary relay PR of first selector E four times. Four impulses are thereby transmitted by said primary relay PR over the previously described path including the upper heavily marked conductor. 108 and through the winding of impulse repeating relay IE to battery. The said relay IR in response to the said four impulses, is energized four times interrupting the circuit through primaryrelay' PR, of second selector Gr four tiincsi' The said, relay PR of second selee-tor G in response to the said four inter ruptions transmits four impulses of current from ground at alternate contact 138 of relay fill through contact 139 and the winding of secondary relay SRto battery, energizing said relay SR which retains its armature in its attracted position until the f said. 1 impulses have. 'been transmitted through. its winding. The said impulses also serve to operate primary magnet PM of third selector H over a path traced from ground at said alternate contact 138, normal contact 140, conductor 141, normal contact -157, wiper 37, contact 40, normal contact 158 of the secondary oil-normal switch SON through the winding of said primary magnet PM to battery. The primary magnet PM responsive to the said four im-- pulses advances wipers 42, 43 and 44 to a point adjacent the fourth group of bank contacts which lead to connector switches having access to the group of one hundred lines which includes the line of called line B. The next step is to pick out an idle one of these connector switches.

After the last primary impulse has been transmitted from primary relay PR of second selector G, secondary relay SR is deenergized, transmitting a secondary impulse from ground at contact 147 of relay 148 at second selector Gr, through impedance coil mal contact 160, wiper 38, contact 41, alternate contact. 161, normal contact 162, and through the winding'of busy relay BR to battery. The said relay BB is thereupon energized closing a circuit" through secondsteps the. wipers .42, 43 and 44 into. engage-- ment with the first set of contacts in the 149, normal contact 150, conductor 159, nor- I selected group and in which contacts -15, 46 and 17 are located. If the first set of contacts 45, 46 and 47 lead. to a busy connector switch J, contact -15 of the said first set is grounded or in a busy condition, as will be lected connector switch, the relay BB remains locked, maintaining the circuit through secondary magnet SM which advances wipers 42, 43 and 44 until a set of contacts 45, $6 and 47, leading to an idle connector switch J are reached.

Assuming switch J is the first idle connector switch in the group, its private contact 45 will be ungrounded and in an idle condition and the locking circuit for relay BR will be interrupted and the said relay BR- will deenergize, opening the circuit through the secondary magnet SM at the contact 163. The wipers 42, 43 and -l-l will therefore remain in connection with the contacts 45, 46 and 47 which lead to connector switch J. Upon the deenergization of the relay BR a grounded or busy condition is placed upon contact 45 and its multiples, traced from r 171, normal contact'172, normal. contact 174 ground at normal. contact 167 of said relay BB through normal contact 166, normal contact 165, wiper 42 to the contact 45 and its multiples, rendering the said connector switch iinseleetable by any other selector having access thereto. The cit-normal spring operation of third selector Haa-nd the cotiperation with the busy relay BB and primary magnet PM is similar to the first and second selector switches. 45

The subscriber at A has now extended his line to the connector J and the said connector J having access to the one hundred line group with which the line of the called subscriber B is associated, the next,- step is to operate the said connector switch J to connect with the called line. The calling subscriber now operates the calling device 3 to transmit five impulses. Res onsive to the actuation of the said calling dgvice 3, the primary relay PR of second selector G is operated five times to transmit five impulses from the ground at alternate contact .138 oi relay R-R over the previously described path, energizing the secondary relay SR in the usual manner and the said impulses flowing over the previously described path to wiper 37, contact 40, normal contact 170, wiper e3, contact 46, conductor of switching relay SKY through the winding of primary magnet PM- to battery, operating the said magnet five times. Responsive to the five operations of said primary magnet PM wipers 48, 49 and 50 are stepped to a point adjacent the fifth group of contact sets, which is the ten group which includes the terminals or bank contacts 51, 52 and 53 of the called subscriber at B. After the last of said primary impulses has been transmitted from primary relay PR, secondary relay SR" is deenergized in the usual n'ianner, transmitting an impulse over the lower heavily marked conductor to wiper 38 and contact 41, normal contact 17 5, wiper 44, contact 47, primary oil-normal contact 176, which is now closed and through the wind ing of switching relay SW to battery, energizing the said relay which looks itself through contact 177 to ground at normal contact 178 of release relay RR. Upon the energization of said switching relay SW, the contact 174 is moved to its alternate position, disconnecting primary magnet PM and connecting secondary magnet SM to said contact 174.

The calling subscriber having now picked 'out the group of ten lines with which the line of the called subscriber is associated, the

next step is tp actuate calling device 3 to transmit six impulses. actuation (of the calling device 3, the primary relay PR of the second selector G is operated six times. transmitting six impulses over the previously described path, energizing the secoiidary relay SR as before, the said impulses also flowing alongthe upper heavilymarked conductor to wiper a3, contact l6, normal contact 172, alternate contact 174, and then through the winding of secondary magnet SM to battery, operating the said secondary magnet six times and stepping the Wipers 48, 49 and 50 into engagement with contacts 51, 52 and 53 which are the sixth set of contacts in the group and are the terminals otthe line of the called subscriber at B which we have assumed is number 23456. The connection from the calling to th called subscriber along the heavily marked conductors is only interrapt-ed at relay 208 of connector J and relay Responsive to the v ondary off-normal switch SON which closed upon the first secondary step of connector switch J, normal contact 180 through the lower winding of test relay-TR to battery, energizingsaid relay TR. Assuming that the called line is busy, there will be aground or busy condition upon multiple con tacts 51, either from a connector switch, if the line is a callediline, or, as previously described, from ground at contact 83 of a line rela 173 to batter ener izim said rela 3 b b J 173 which is then looked through alternate contact 184: to said ground at normal contact 178. The energization of said relay 178 disconnects test relay TR from the lower heavily marked conductor, and secondary magnet SM from the upper heavily marked conductor. "Although at this time the contact 185 of the relay 173 is closed, the circuit extending through the said contact is opened at contact 181 of the relay TR. Responsive to the energization of the test relay TR, its contact 186 is closed connecting the busy back signal BB with conductor 171 and transmitting said signal to the calling subscriber over a path which includes the upper heavily marked conductor back through third selector H, second selector G, over the trunk pircuit F, to normal contacts 130, 129, the winding of relay 31, alternate contact 125, over the lower heavily marked conductor through first selector E, line selector D,lin e circuit C, the line conductor 1, the receiver of substation A, returning over line conductor 2 along the upper heavily marked conductor of line circuit 0, line selector D, conductor 91 of first sclector E, normal contact 90 -and the upper winding of relay PR to ground. Although the busy signaling current will be shunted by the prlmary relays, this shunting effect is not sufficientto prevent apprising the calling subscriber of the state of the called line. The said busy back signal which is a well known characteristic signal, being received by the calling subscriber, the said subscriber is notified that the called line is busy and therefore replaces the receiver 11 upon its switch hook 8. The replacing of the rcceiver 11 upon its switch hook is eiiective to restore all of the switches used in establishing the connection and is also eilective toconnect the polarized relay 57 of the coin erated.

As the called subscriber was busy, the coin or token which was placed in the slot is returned to the calling subscriber, this being accomplished in the following manner: lVhen the receiver is placed upon switchhook 8, the shunt which existed across the terminals of the winding of the polarized magnet 57 is removed by the opening of contact 58 and switch-hook 8. Current from priiiiary relay PR of the first selector E which flowed through the telephone or" the calling subscriber at A now flows through the winding of polarized magnet 57,. due to the shunt being removed, this flow being in such a direction that the armature 55 is attract'ed toward the left. This allows the coin or token which has been deposited in the slot 54 to drop out of the slot 5% which conducts the coin out of the usual coin box to be returned to the calling subscribe-r. The coin or token having moved out of engagement with insulating stud 56, contact spring 7 is restored to its normal position, disconnecting polarized magnet 57 from circuit with the line, thus interrupting the circuit through the substation A at contact 7. The circuit at the substation A being interrupted, the primary relay PR of first selector E deenergizes, retracting its immature and restoring its contact springs to normal.

The opening of contact 95 of primary relay PR allows release relays RR of line selector D and RR of first selector E to deenergize. Upon the deenergization of release relay RR of line selector D, a circuit for relay SBR is established from ground at contact 190, alternate contact 79 of seconddary off-normal switch SON, through the winding of relay SBR to battery, energizing said relay SBR. Responsive to energization of said relay'SBR, a circuit for release magnet R-M is established from ground at alternate contact 80 of said relay SBR, normal contact 81 of release relay RR, through the winding of said release magnet RM to battery, energizing the said magnet which with-' draws the retaining pawls of the wiper shafts, and wipers 16, 17 and 18 restore to normal. ,lpon the energization of release magnet RM, the circuit through cut-ofl relay CO is interrupted at contact 82 of said magnet RM and said relay CO deenergizes, restoring the line circuit C to normal. The secondary relay SBR has its energizing circuit switches at the time the secondary oil":

alternate to its normal position. to ground at normal contact 76, this circuit being interrupted at contact 78 of switch PON, and said relay SBR retracts its armatures. It

normal switch contact 79 is moved from its will thus be seen that while the wipers 16, I

17 and 18 are being restored and moving over the bank contacts they are disconnectthemaster switch K. is ronnected to grminc at line selector 1.) through alternate contact 82 and alternate conta t 8%. thus"maintaining contact 86 of master switch 1:: grounded or busy from line selector l) until said switch I) has been restored to normal.

Returning now to the release o't first selector E. upon the decnergization of its release relay RR. a circuit tor relay BB is established from ground at normal contact 105 of said relay RR. alternate contact 115 of primary oil-normal switch PON, through the winding of said relay HR to battery. energizing said relay BR. Responsive to the energization of said relay BR. a circuit for release magnet FM is established troni ground at alternate contact 192. normal con tact 117 of the release relay RR, through the winding of said release magnet RM to battery. energizing slid u'iagnet RM and withdrawing the retaining pawls. allowing wipers 25. 2G and 27 to restore. Also, upon the deenergization of release relay RR. the locking circuittor relay of trunk circuit F is opened. allowing said relay 33 to deenergize. This istor the purpose of releasing' the other switches which will he hereinafter more tully explained. Upon the restoration of first selector Eathe primary oil-normal switch PONHnoves its contacts to their normal position. thereby opening the preyiously described circuit through the relay BR at the contact 115. allowing .sa-idt relay BR to de'encrgize and open the circuit tor releasemagnet RM which also deenergizes.

-As previously stated. the conductor 85 leading to the master switch K is maintained grounded until the line selector l) releases. This conductor is also maintained grounded until the first selector switch. E restores to normahby means of the ground'at primary .ofii-nornial switch POR Thus. it will be seen that the contact 86. of the master switch K is maintained grounded or busy until its associated connected pair of switches are restored to normal. I

Returning now to relay I-lil'ot' trunk circuit F, it will be remembered that the said relay deenergizing uponthe energization of the release relay RR of the first selector li. The opening of contact 12.) of said relay 3 interrupts the circuit through primary relay PR of second selector G and the said primary relay de'nergizes retracting its armature. The release relay RR of second selector G is thereupon deenergized. due to the opening of its energizing circuit at the. contact 135 of relay PR and said release relay Rit retracts its armatures restoring its contacts to normal. Upon said dctnergization of release relay RR a circuit tor the relay 13B is established from ground at normal contact 138 of relay llll". contact 19st of primary oil-normal :-\\it(l1 PO). through the winding of said relay BB to battery, causing its energization. Responsive to the said energization of relay BB a. circuit through release magnet BN is established from ground at alternate contact 153 of relay BB normal contact 151 'e'l relay RR. through the winding of the normal contact 154" of release magnet RM? wiper 36. contact 39. alternate contact 195 of primary cit-normal switch P0X of third selector switch H, through the winding of said release. relay RB to ground. energizing said release relay BB 4 Returning now to second selector G. re lease magnet RM having been energized as described. .the circuit just traced through release relay RR of third selector H is interrupted at contact 154 of release riagnet RM thus opening the initial energizing circuit for said relay RR Upon the Said cnergization or release magnet RM the re taini'ng pawls tor the second selector switch (l are withdraun. allowing wipers 36, 37 and 38 to restore to normal. As relayfBR of said switch (l remains energized until its circuit is opened at primary oft-normal switch PON wipers 37 and 38 remain dis connected at contacts 157 and 160 of said relay BB ,On the restoration of said switch G to normal, the circuit for relay The release relay RR of third selector H having been energized bythe impulse oi current'trom second selector G. a locking circuit for said relay RR is established from ground-through; the winding of said relay Ell alternate contact 195. alternate contact 196. conductor 197. throl'lgh the windingot relay BR" to battery. maintaining saul rclay Till energized and thesaid circuit also energizing relay BR". Upon the said energization of relay Rll a ,I'eleasing impulse is transmitted to connector J From battery.

at alternate contact 166 of said relay RR, normal contact 165, of release magnet RM, wiper 42, contact 45, conductor 198, contact 199, through the winding of release relay RIB of connector J to ground, energizing said release relay RE.

The release relay BB and relay BR of third selector H having been. energized and locked up in series, a circuit for the release magnet RM is established from ground at alternate contact 163 of relay BB alternate contact 164 of relay RR", through the winding of release magnet RM tobattery, energizing said magnet RM which withdraws the retaining pawls of third selector switch H, allowing wipers 42, 43 and 44 to restore to normal. During the restoration of the said wipers, wiper 42 has its circuit opened at contact 165 of said release magnet RM and Wipers 43 and 44 have their circuits opened at the contacts 170 and 175 of relay BR. On the restoration of said switch H to normal, primary off-normal switch PON is restored to normal, opening the series energizing circuit for relays RR and BR at contact 195. The said relays are thereupon deenergized, opening the circuit 'for release magnet RM. The third selector switch H. and its associated mechanism is now at normal and available for further use.

The release relay RR- of the connector switch J having been energized from an impulse of current from third selector switch H as described, a. locking circuit for said relay RR is established from ground through the winding of said relay RR. al-

ternate contact 199 of switch PON, con ductor 198, conductor 200, alternate contact 201 of relay RR, through protective resistance 202 to battery. Upon the said err ergization of relay RE, the locking circuit for relays SW and 173 is opened at contact 178,. the said contact then closing a circuit through release magnet RM, energizing the said magnet. Upon the said energization of release magnet RM, the retaining pawls for the connector switch J are withdrawn. allowing wipers 48, 49 and 50 to restore to normal. The connector switch J and its associated mechanism now having been restored, the said switch is available for fur-.

ther use. I

The swltches and all their associated mechanism WhlCh were used in establishing the connection from the line of the calling subscriber at A to the line of the called subscriber at B have now been restored to normal and are available for use in establishing other connections.

Called Zine idZe.-Assuming now that the calling subscriber has extended his line to terminals 51,52 and 53 of the line of the called subscriber at B, and thatthe said line is-idle, the last secondary impulse as previously described, energizes test relay TR of connector switch J. Having assumed that the called subscriber is idle, there will;

the said energization of relay TR, a circuit for relay 173 is established from ground at normal contact 178 of release relay RR, conductor 182, alternate contact 183 ofr-elay TR, through the Winding'of said relay 173 to battery, energizing said relay 173 and establishing a ldcking circuit for it through contact 184 to the said ground at normal contact 178. On the energization of the relay 173, the circuit through the lower winding of the test relay TR is interrupted at contact 180, allowing the said relay to deenergize. The opening of contact 172 of relay 173 disconnects secondary magnet 81W from the upper 'talking conductor. Also, upon the ener ization of relay 173 and deenergization of relay TR, a circuit for relay 204 is established from ground through the winding of said relay 204, alternate contact 185, normal contact 181, wiper 48, contact 51, normal contact 64' of line relay LR, the winding of cut-01f relay CO to battery, energizing both of the relays 204 and CO.

The energization of cut-ofi' relay CO removes the substation control of line relay LR. Upon the energization of relay 204, a circuit is stablished from ground at normal contat 178 of relay RR, conductor 205, alternate contact 206, normal contact 207 of relay 208, through the Winding of the generator or ringing relay GR to battery at the interrupter wheel I. w

The interrupter Wheels I and I are preferably mounted upon the same shaft, being rotated by a motor or in any desirable way. The relay GR energizes responsive to the closing of the circuit just described, thereby connecting ringing generator G with the called line through the lower segment of the interrupter I and its brush, alternate contact 209, of relay GR, wiper 50, contact 53, line limb 1', through the condenser and call bell of the called subscribers telephone B, line limb 2, contact 52, wiper 49, conductor 210, alternate contact 211, through the winding of coil 212 and battery to ground, operating the bell of the subscribers telephone B.

The bell of the called subscriber is intermittently rung due to the interruptions of the circuit through the ringing relay G-R at the interrupter 1. Due to the construction and relative position. of the interrupter wheels I and I, the circuit from generator G is interrupted at wheell before the energizing circuit for the relay GR is interrupted at wheel I. The ground connection to the upper segment of interrupter wheel I from the current from ringing generator G.

If the line were not discharged to ground as described, there would be a tendency for the line to discharge through relay 213, operating it prematurely. The interrupter Wheels 1 and 1' continue int-heir rotation until the insulated segment of the wheel I engages its brush and the circuit through the relay GR being interrupted, the said relay dcenergizes, Upo the said deiinergization of relay GR, relay 213 is connected to the called line through alternate contact 214 01 relay 20%}, normal contact 209 of relay GR to the Wiper 50, contact 53, and the limb 1 of the telephone line. Assuming the subscriber has not responded to the call, the circuit through the telephone B for direct current is interrupted at the condenser 10 that the relay 213 is not energized. The interrupter wheels I and I continuing in their rotation, generator G and relay 213 are alternately connected through contact 209 of relay GR to the called line. Y

The called subscriber responding to the call, removes receiver 11" from its switch hook, thereby disconnecting call. bell 9 and establishing a path for direct current through the upper contacts of the switch hook 8'. A circuit for relay 213 is there fore established when the relay GR- .is decnergized, from ground, through the Winding of said relay 213, alternate contact 214, normal contact 209, Wiper 50, contact 53, line limb 1, the Winding of cello, upper contacts of switch hook 8, transmitter 12,

, limb 2. contact Wipers i9. conductor 210 alternate contact 211, impedance coil 212 to battery. The relay 213 is thereupon encrgized over the path just described, said rel a now being under the control of the called subscriber, it being energized over a path including .the line of called subscriber B. Upon the said energization of relay 213, a circuit for relay 208 is established from ground at normal contact 178 of relay RR, conductor 182, conductor 205, alternate contact 206, alternate contact 215, conductor 21?. winding of relay 208 to buttery. eucr gizing said relay 208. Upon the said enc-r-- gization of relay 208, the circuit through ringing relay GR- is'interruptcdnt contact 207. said relay 208 then looking itself through said contact 207, contact 206, conductor 205,

conductor 182, to groinid at normal contact 178. The closing of contacts 218 and 219 of rela y 208extend the connection from the connector switch 3 to the line of the called subscriber at 18. Upon the said response of iPON the called subscriber and the energization of the relay 208 of connector J, a circuit for relay 148 of second selector sw1tch G as established from ground at relay 213 of con- I nector J, contact 214, normal contact-209, Wiper 50, contact linc limbs 1, and 2', and the telephone of substation B, contact 52, Wiper 19, contact 218, along the upper heavily marked conductor, through the Wipers of switches J and H to contact 40 and Wiper 37 of switch G normal contact 157, alternate contact 140 of relay PR, norv.uml contact 220 of relay SR, the Winding of relay 148 to battery, energizing said relay 148. The said energization of relay 1 18 is effective to operate reversing relay RV which reverses the flow of battery current through the polarized relay 31 of trunk circuit F which, operating in response to the said reversal, is eli'ectire to close the circuit of the upper heavily marked conductor of the relay 32 at trunk circuit F, in response to Which the reversing relay RV of the first selector switch E is operated.

The operation of the said reversing relays and polarized relay which occurs only when a called subscribr responds, is brought about as follows: Upon the said energizetion of relay 1218 of second selector G, a circuit for reversing relay RV is .established from ground at alternate contact 221, through the Winding of said relay RV to battery, energizing said relay RV, which locks up through alternate contact 145 to ground at alternate contact 144 of switch The said energization of relay RV reverses the flow of battery at contacts 222 and from primary relay PR, through polarized relay 31 of trunk circuit F.' This said reversal of current through polarized relay 31 is eilective to attract its armature 13-1 upward,- closing a circuit through relay 32 from ground at alternate contact 13%. The said relay 32 is thereupon energized closing the alternate contact 137 and establishing the continuity of the upper heavily marked conductor. Also, upon said ener; gization of relay RV. of second selector switch G, the circuit for 14-13 is interrupted at contact 115. The-said relay 143 is therefore de'cnergizcd, closing contact 1&6 and es blishing a circuit through relay 127 from grcund at contact 225 of relay 82, of trunk circuit F, through the winding of the lower coil of polarized relay 31, alternate contact conductor 35, normal contact 1 16, the winding of said relay 127, alternate contact 220, impedance coil 227, conductor 34, alternate contact 13?, contact 2 wiper 20, normal contact 136, conductor 108, normal contact 107, normal contact 228, through the winding of relay 229 to battery. This circuit is effective to retain the armature of the polarized relay 31 in its upward position and to energize relay 127 of second selector G and relay 229 of first selector E, the three said relays being in series. The said energization of relay 127 opens normal contacts 133 and 126 and establishes a locking circuit for relay PR from ground to alternate contact 133.

The release relay RR of second selector switch G which had its, initial energizing circuit opened at normal contact 136 of re lay RV is maintained energized over a circuit from ground at alternate contact 147 of relay 148, alternate contact 136 of relay RV. through the winding of the said relay BB to battery. At second selector switch G, the relays RV, 127, PR, BB and 148 are now all energized, remaining so until the subscribers replace their receivers upon their switch hooks upon the completion of conversation.

At first selector switch E, relay 229 havmg been energized as described, a circuit for revversing relay RV is established from ground at alternate contact 105 of relay RR, alter-.

nate contact 106, normal contact-111, alternate contact 112, winding of the said relay RV to battery, energizing said relay RV which looks itself through contact 230 to ground at the primary ofl"-normal switch PON or ground at line selector D. Upon the said energization of relay RV the initial energizing circuit for release rela RR 15 opened at contact 104 of relay R but the relay 229 having been energized, a new path is established through its contact 321. The opening of contact 104 of relay RV places release relay RR under control of the calling and called subscribers, as will be more fully described.

The closing of the contacts 232 and 233 of relay RV reversed the flow of battery current from the primary relay PR over the line of the calling subscriber. This reversal of battery flow is efi'ective to operate the polarized magnet 57 to collect the coin or token of the calling subscriber when receiver 11 is replaced upon switch hook'8 at the termination of the conversation. The con' nection from the calling subscriber to the called subscriber is now completed, the talking circuit being traced over the heavily marked conductors. Talking battery for the calling subscriber-is su plied from battery at primary relay PR 0 the first selector E, Talking batter for the called subscriber is supplied from attery at impedance coil 212 of connector J over the previously described path including the called line and telephone to ground through the winding of relay 213 of connector J. 4

The condensers 235 and 236 at first selector E and condensers 237 and 238 at second selector G inductively unite the talkin' Leonductors between the callingand calle subscribers. Battery is bridged across the talk I mg conductors of trunk circuit F during a ily marked conductorto switch G, impedance coil 227,- alternate. contact 226, relay 127, normal ,contact, 146, the lower heavily marked conductor. 35 .to alternate contact 125 at trunk circuit F, the winding of the lower coil of relay 31 to ground at alternate contact 225. v I

ReZease.On finishing conversation, the

subscribers replace their receivers on their respective switch hooks. Should the calling subscriber at A be the first to replace his 30 receiver upon its switch hook, all of the switches used in establishing the connection except the connector switch J will release. Should the called subscriber at B be the first to replace his receiver upon its switch book, all of the switches except the line, selector D will release;

Assuming that the called subscriber at B first restores his receiver to. its switch hook,

. the previously traced energizing circuit for relay 213 of the connector switch. J is interrupted at the contactsof the switch hook I 8:. The said relaiy 213, therefore deener= gizes, but has no e ect upon any. of the 0111 cuits at this time. e

, r 7 It will be remembered that relay 148 of second selector G has been maintained energlzed over the previously descrlbedc'ircuit from ground through the winding or relay 213 over the limbs of the'called, telephone line B and .back along the upper heavily marked conductor to said relayj148. This energizing circuit for therelay 148 is inter- 1 rupted when the subscriber at B laces his I'BCGIVBIVUPOH its switch book an said relay 1 13 .deenergizes; U p'on' the said deenergizatlon of relay 148, the energizing circuit through release relay RR of switch G is interrupted at ground through alternate contact 1 17 of relay 148. The said'release relay 11 RR therefore deenergizes and a circuitfor relay BR is established from round at normal contact 1380f said relay R alternate. contact 194.- of switch PON through the winding of said relay BR- tolbattery. The 1 sa1d relay BR is thereupon energized, clos mg a circuit through releasejmagnet RM,

energizin the said magnet; The release r elay- RR iaving deenergized previous to ,the

the release magnet RM anenergizatio-n o impulse of current is transmitted from; at-

tery at normal contact 155 of-re'lay RRfto releasing relay RR of third selector H. The} energization of the-release magnet RM'of the second selector G restores the switch as 1 previously described and the energization er the release relay BB of third selector H- is efiiective' lgo' operate therelease magnet of they said switch. to restore-,its .wipers as previously SWibGd Upouthersaid energize,

- will be remembered that the relay 229 there I tion of release relay RR "of switch H, an energizing circuit for the release relav RR of connector switch J is established from battery at alternate contact 166 of said relay EH normal contact 165, wiper 42, con tact .5, conductor 198, alternate contact 199, the winding of said relay BB to ground. The relay RR is thereupon energized opening the circuit for switching relay S /V and relay 173 as previously described in connection with the release and said relays SW and 173 deenergize. Upon the deenergization of relay 173, the energizing circuit for relay- 204 and cut-oit relay CO is interrupted at contact 185 of said relay 173 and said relays 20a and COdeenergize. The deenergization of the relay 20% opens its contact 206. thereby opening the energizing circuit for relay208 which now deenergizes, retracting its armature and restoring its con tacts. Also", upon the energization 'of release relay R11 a circuit for release magnet RAP is established as previously described, resulting in the encrgization of the said release magnet and the restoration of the connector switch J.

Returning now to switch G, the relay 148 having deenergized upon the restoration of the called subscribers receiver upon its switch hook as described, the connection from the upper talking conductor 34 to the lower talking conductor 35 is interruptedat contact 226 of said relay 148, interrupting the circuit for polarized relay 31 of trunk circuit F and relays 127 of switch G and 229 of switch E. The said relay $1 is therefore denergized, opening the circuit for relay 32 at contact 134 and said relay 32 denergizes, restoring its contact springs to normal. The slow-acting relay 127-01 s'witch G having also been included in circuit with the polarized relay 31, now retracts its armature, openingthe circuit for the primar relay PR at alternate contact 133, allowing the said relay PR to deener 'ize. The reversing relay RV has its energizing circuit opened at contact 1% of the switch PON upon the restoration of the switch G and retracts its armature. The switch G and all of its associated mechanism is now at normal.

Referring now to the first selector E, it

of was included in the circuit of relay 127 of switch Gr and relay 31 of trunk circuit F, and the said circuit having been interrupted as previously described at contact 226 of relay 1&8 of secondary selector G, said relay 229 deZ-Snergizes. 'Upon said deenergization of relay 229 the circuit for release relay RR of switch E is interrupted at contact 23 of relay 229,. and said relay RR deenergizes, interrupting the circuit for relay 33 of trunk circuit F which restores to normal. Also, upon the deenergization of relay RR, relay BR and the release magnet RM of switch I ing of its contact E are energized aspreviously described, resulting in the release of the said switch E as previously described. T lie-calling subscriber at A now by replacing his receiver upon its switch hook, connects the polarized magnet 57 of the coin controlling device into circuit with the line.' The calling subscriber at A having received a. response from the called subscriber and the reversing relay RV of stud 56, spring 4 moves t'o'normal, interrupting the circuit for battery flow throughsubstation A as previously described, thereby interrupting the circuit for primary relay PR of switch E, denergizing said relay PR. Upon the said deenergization of relay PR the'energizing circuit for release relay RR of line selector D is interrupted at ground at contact 95 of relay PR, de'energizing said relay RR. The said denergiza-- tion of relay RR is effective to energize relay SBR and release magnet RM, resulting in the restoration of line selector 1) and the line circuit C, as previously described.

The reversing rela RV of switch E is maintained energize through its locking contact 230.to the ground connected to'conductor 85 which maintains the contact 86 of the master switch K busy. Therefore, the said relay RV deenergizes upon the restoration of the line selector D when the said ground connections to the conductor 85 are removed. All the switches used in establishing the connection from the calling subscriber at A to the called subscriber at B have now been restored to normal and are available for further use.

Assuming now that the calling subscriber at A is the first to replace his receiver upon its switch hook, line circuit C, line selector 1). first selector E, trunk circuit F, second selector D, and third selector H are released. Responsive to the placing of receiver 11 upon its switch books at the calling substation A, the circuit for primary relay PR of switch E is interrupted, said relay PR deeuergizinr and interrupting the circuit for release relay RR by the open- The opening of said contact 95 also interrupts the energizing circuit for release relay RR of line selector D. said relay RR also deenergizing. Upon -the deenergization of said two release rclays. their respective switches and line circuit E are-released as previously descril .Also, upon the deiinergization of relay PR.

the series circuit, including relays 229,

rats

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